282 TRIASSIC PLANTS FONTAINE AND KNOWLTON. 



stratum of reddish due j^raiued sandstones, also about 200 feet in 

 thickness, the whole being capped by a layer of coarse-grained, yel- 

 lowish sandstones 150 feet or more in thickness. 



In some places the second of the above mentioned strata has the 

 sandstone of a yellowish or nc'^rl}^ white color, and it is in this material 

 on the eastern side that the old copi)er mines are located. There are 

 but three openings visible at the present time. The openings are 5 or 

 6 feet square and descend at a slight angle, the deepest being only about 

 75 feet. Ouly one is branched, and none of them are braced up with 

 timbers at the present time. At the time the mines were visited by Dr. 

 Newberry they were braced up with heavy timbers, and there was evi- 

 dence of quite an extensive series of tunnels. It is possible tliat the 

 mines visited are not the same as those mentioned by Dr. Newberry, as 

 they have been recently worked, and exhibit none of the evidences of 

 great antiquity noticed by him, but these were the only mines known to 

 the guide, who was a native of Abiquiu, and had worked in the mines. 

 The coijper occurs as a sulphide of copper and iron, and as iron car- 

 bonate, and is distributed thr^jugh a layer hardly more than 4 feet in 

 thickness. It has replaced the trunks of trees and various vegetable 

 stems and fragments, and also occurs in concretions about and among 

 the quartz pebbles. 



Just above the openings of the mines occurs a layer of carbonaceous 

 shale, about 8 inches in thickness, which contains fossil plants. The 

 material splits very readily into thin laminae and is very fragile. The 

 surface of the shale is covered with such a mass of vegetable impres- 

 sions that it is with considerable difficulty that anything can be made 

 out; but by removing a considerable quantity of the material a fairly 

 clear display of the plants was obtained. 



From the same white sandstone, about 10 feet above the shale hold- 

 ing the plant impressions, considerable fossil wood was obtained. One 

 trunk, which was 2 feet 8 inches in diameter, was observed in place in 

 the sandstone, and numerous pieces of greater or less size were scat- 

 tered about. While only one trunk was actually found in situ there is 

 every evidence to indicate that the loose pieces came from the imme- 

 diate vicinity. The wood is fairly well preserved and, as ihe microscop- 

 ical examination showed, retains the structure in a manner which 

 allows its satisfactory study and determination. 



The new copper mines, which were opened during the spring of 

 1889, are in the northwestern part of the basin. They are located in 

 a white very coarse-grained sandstone which, as there exposed, forms 

 the floor of the basin and is consequently several hundred feet lower 

 than the old mines. The copper occurs in the form of wood or stems 

 only. Some of the stems bear evidence of having been large but are 

 now considerably disintegrated. The structure has almost entirely 

 disappeared from these stems, but a carefully selected section shows 

 traces of it to be still retained. 



